jeudi 17 mai 2012

May 17 to 23 hours 12 minutes Moscow time from Launch Complex 81 area businesses calculations Baikonur space industry made ​​launch a space rocket Proton-M with the upper block (RB) the Briz-M, designed for launching into orbit telecommunications space vehicle (SV) Nimiq 6.

Launch of Nimiq-6 on Proton-M Rocket

The three stages of the Proton vehicle have performed as planned, and it is up to the Breeze M upper stage to complete the mission.

In accordance with the flight cyclogram head unit in the Republic of Belarus the Briz-M and SC Nimiq 6 cleanly separated from the third stage of the launch vehicle, followed by removal of the SC RB continued to the target orbit.

Nimiq 6 Satellite

Nimiq 6 is a Direct Broadcast Satellite built by Space Systems/Loral. The satellite has a 32 transponder Ku-Band payload providing coverage of Canada. The satellite will be located at 91.1° west longitude. This satellite will be dedicated to the provision of direct-to-home services as part of Telesat’s DTH fleet.

The launch vehicle flew smoothly, and, at about 16 minutes and 3 seconds after liftoff, the separation of the KOMPSAT-3, then at about 22 minutes and 59 seconds after liftoff, the separation of the SHIZUKU were confirmed respectively.

The GCOM-W (Global Change Observation Mission - Water) or Shizuku

Also we confirmed that the launch vehicle sent separation signals to the small satellites (SDS-4 and Horyu-2) as planned.

We would like to express our profound appreciation for the cooperation and support of all related personnel and organizations that helped contribute to the successful launch of the H-IIA F21.

At the time of the launch, the weather was fine, a wind speed was 4.9 meters/second from the west-north-west and the temperature was 18.7 degrees Celsius.

Image above: Hot stars burn brightly in this new image from NASA's Galaxy Evolution Explorer, showing the ultraviolet side of a familiar face. Image credit: NASA/JPL-Caltech.

NASA is lending the Galaxy Evolution Explorer (GALEX) to the California Institute of Technology (Caltech) in Pasadena, where the spacecraft will continue its exploration of the cosmos. In a first-of-a-kind move for NASA, a Space Act Agreement was signed May 14 so the university soon can resume spacecraft operations and data management for the mission using private funds.

"NASA sees this as an opportunity to allow the public to continue reaping the benefits from this space asset that NASA developed using federal funding," said Paul Hertz, NASA's Astrophysics Division director at the agency's headquarters in Washington. "This is an excellent example of a public/private partnership that will help further astronomy in the United States."

Image above: A speeding star can be seen leaving an enormous trail in this image from NASA’s Galaxy Evolution Explorer. Image credit: NASA/JPL-Caltech.

The Galaxy Evolution Explorer spent about nine years as a NASA mission, probing the sky with its sharp ultraviolet eyes and cataloguing hundreds of millions of galaxies spanning 10 billion years of cosmic time.

"This mission was full of surprises, and now more surprises are sure to come," said Chris Martin, who will remain the mission's principal investigator at Caltech. "It already has scanned a large fraction of the sky, improving our understanding of how galaxies grow and evolve. The astronomy community will continue those studies, in addition to spending more time on stars closer to home in our own galaxy."

This image of the Cartwheel galaxy shows a rainbow of multi-wavelength observations from NASA missions. Image credit: NASA/JPL-Caltech.

The spacecraft was placed in standby mode on Feb. 7 of this year. Soon, Caltech will begin to manage and operate the satellite, working with several international research groups to continue ultraviolet studies of the universe. Projects include cataloguing more galaxies across the entire sky; watching how stars and galaxies change over time; and making deep observations of the stars being surveyed for orbiting planets by NASA's Kepler mission. Data will continue to be made available to the public.

"We're thrilled that the mission will continue on its path of discovery," said Kerry Erickson, the mission's project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "The Galaxy Evolution Explorer is like the 'little engine that could,' forging ahead into unexplored territory."

During its time at NASA, the Galaxy Evolution Explorer made many discoveries involving various types of objects that light up our sky with ultraviolet light. Perhaps the most surprising of these was the discovery of a gargantuan comet-like tail behind a speeding star called Mira. Other finds included catching black holes "red-handed" as they munch away on stars, spying giant rings of new stars around old, presumed dead galaxies, and independently confirming the nature of dark energy.

For astronomers, the most profound shift in their understanding of galaxy evolution came from the mission's findings about a "missing link" population of galaxies. These missing members helped explain how the two major types of galaxies in our universe -- the "red and dead" ellipticals and the blue spirals -- transition from one type to another.

"We were able to trace the life of a galaxy," Martin said. "With the Galaxy Evolution Explorer's ultraviolet detectors, we were able to isolate the small amounts of star formation that are the signatures of galaxies undergoing an evolutionary change. We found that galaxies don't have a single personality, but may change types many times over their lifetime."

Image above: A galaxy sprouts stars far from its central hub, as seen here where the blue dots line the red, spindly, spiral arms. Image credit: NASA/JPL-Caltech/VLA/MPIA.

Under the new agreement, NASA maintains ownership and liability for the Galaxy Evolution Explorer spacecraft. When Caltech completes science activities, it will decommission the spacecraft for NASA. The mission's batteries and solar panels have an expected lifetime of 12 years or more, and the spacecraft will remain in orbit for at least 66 years, after which it will burn-up upon re-entry into Earth's atmosphere. The agreement can be renegotiated when it expires in three years.

Orbital Sciences Corporation in Dulles, Va., which built the spacecraft, will continue performing flight control functions for Caltech associated with monitoring and commanding GALEX and participating in mission planning. Universal Space Network will continue providing the ground stations for communicating with the spacecraft.

Expedition 31 crew members Gennady Padalka, Joe Acaba and Sergei Revin were welcomed aboard the International Space Station after the hatches opened Thursday at 4:10 a.m. EDT. They docked to the Poisk module at 12:36 a.m. after a two day journey that began in Baikonur Cosmodrome, Kazakhstan aboard a Soyuz TMA-04M spacecraft.

After a series of leak and pressure checks, Expedition 31 Commander Oleg Kononenko and Flight Engineers Don Pettit and Andre Kuipers welcomed their new crewmates.

The new trio joined the crew for a greeting ceremony and conference with family and mission officials then conducted a safety briefing afterwards. It is now back to business for the current station residents while their newly arrived crew mates begin several days of familiarization tasks as they adjust to life aboard the orbital laboratory.

The docking occurred on Acaba’s 45th birthday. He previously visited the station in March 2009 aboard space shuttle Discovery as an STS-119 mission specialist. This is Padalka’s fourth long-duration spaceflight and his third aboard the station. His first mission was aboard Russian Space Station Mir. Revin is making his first trip into space.

Padalka is due to become Expedition 32 commander when Kononenko, Pettit and Kuipers undock July 1 in their Soyuz TMA-03M spacecraft after a six-month stay officially ending Expedition 31. Expedition 32 will be complemented two weeks later when it is joined by Flight Engineers Suni Williams, Yuri Malenchenko and Aki Hoshide.

While the space station transitions to six-member operations, SpaceX ground controllers are gearing up for the May 19 launch of the Dragon capsule. The first commercial cargo craft is scheduled to launch at 4:55 a.m. with the Canadarm2 grappling Dragon May 22 for a berthing to the Harmony node.

mercredi 16 mai 2012

Image above: New results from NASA's NEOWISE survey find that more potentially hazardous asteroids, or PHAs, are closely aligned with the plane of our solar system than previous models suggested. Image credit: NASA/JPL-Caltech.

Observations from NASA's Wide-field Infrared Survey Explorer (WISE) have led to the best assessment yet of our solar system's population of potentially hazardous asteroids. The results reveal new information about their total numbers, origins and the possible dangers they may pose.

Potentially hazardous asteroids, or PHAs, are a subset of the larger group of near-Earth asteroids. The PHAs have the closest orbits to Earth's, coming within five million miles (about eight million kilometers), and they are big enough to survive passing through Earth's atmosphere and cause damage on a regional, or greater, scale.

The new results come from the asteroid-hunting portion of the WISE mission, called NEOWISE. The project sampled 107 PHAs to make predictions about the entire population as a whole. Findings indicate there are roughly 4,700 PHAs, plus or minus 1,500, with diameters larger than 330 feet (about 100 meters). So far, an estimated 20 to 30 percent of these objects have been found.

While previous estimates of PHAs predicted similar numbers, they were rough approximations. NEOWISE has generated a more credible estimate of the objects' total numbers and sizes.

This diagram illustrates the differences between orbits of a typical near-Earth asteroid (blue) and a potentially hazardous asteroid, or PHA (orange). Image credit: NASA/JPL-Caltech.

"The NEOWISE analysis shows us we've made a good start at finding those objects that truly represent an impact hazard to Earth," said Lindley Johnson, program executive for the Near-Earth Object Observation Program at NASA Headquarters in Washington. "But we've many more to find, and it will take a concerted effort during the next couple of decades to find all of them that could do serious damage or be a mission destination in the future."

The new analysis also suggests that about twice as many PHAs as previously thought are likely to reside in "lower-inclination" orbits, which are more aligned with the plane of Earth's orbit. In addition, these lower-inclination objects appear to be somewhat brighter and smaller than the other near-Earth asteroids that spend more time far away from Earth. A possible explanation is that many of the PHAs may have originated from a collision between two asteroids in the main belt lying between Mars and Jupiter. A larger body with a low-inclination orbit may have broken up in the main belt, causing some of the fragments to drift into orbits closer to Earth and eventually become PHAs.

Asteroids with lower-inclination orbits would be more likely to encounter Earth and would be easier to reach. The results therefore suggest more near-Earth objects might be available for future robotic or human missions.

"NASA's NEOWISE project, which wasn't originally planned as part of WISE, has turned out to be a huge bonus," said Amy Mainzer, NEOWISE principal investigator, at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Everything we can learn about these objects helps us understand their origins and fate. Our team was surprised to find the overabundance of low-inclination PHAs. Because they will tend to make more close approaches to Earth, these targets can provide the best opportunities for the next generation of human and robotic exploration."

The discovery that many PHAs tend to be bright says something about their composition; they are more likely to be either stony, like granite, or metallic. This type of information is important in assessing the space rocks' potential hazards to Earth. The composition of the bodies would affect how quickly they might burn up in our atmosphere if an encounter were to take place.

The WISE spacecraft scanned the sky twice in infrared light before entering hibernation mode in early 2011. It catalogued hundreds of millions of objects, including super-luminous galaxies, stellar nurseries and closer-to-home asteroids. The NEOWISE project snapped images of about 600 near-Earth asteroids, about 135 of which were new discoveries. Because the telescope detected the infrared light, or heat, of asteroids, it was able to pick up both light and dark objects, resulting in a more representative look at the entire population. The infrared data allowed astronomers to make good measurements of the asteroids' diameters and, when combined with visible light observations, how much sunlight they reflect.

JPL manages, and operates the Wide-field Infrared Survey Explorer for NASA's Science Mission Directorate, Washington. The principal investigator, Edward Wright, is at UCLA. The mission was competitively selected under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory, Logan, Utah, and the spacecraft was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing and archiving take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

Graphic above: The new excited states show clear signals at masses of 5912 MeV/c2 and 5920 MeV/c2 (Image: LHCb collaboration).

The Large Hadron Collider beauty (LHCb) experiment at CERN today announced that it has observed two new excited states of the Λb
beauty baryon. Though the Standard Model of particle physics predicts
the existence of these new states, this is the first time they have been
confirmed in an experiment.

Baryons are subatomic particles whose mass is equal to or greater than that of a proton. Like protons and neutrons, the Λb beauty baryon is composed of three quarks. In Λb these are up, down and beauty quarks.

LHCb physicists found the signals for the Λb particlesin a
sample of about 60 trillion proton—proton collisions which were
delivered by the LHC operating at a centre-of-mass energy of 7 TeV in
2011. They measured the masses of the new excited states as 5912 MeV/c2
and 5920 MeV/c2 respectively - over five times greater than the mass of a
proton or neutron.

CERN,theresearchof the secrets ofthe Universe

The result adds to a growing list of discoveries at CERN in recent
months. Last month the Compact Muon Solenoid (CMS) experiment observed a
new excited state for the Ξb beauty baryon, and back in December 2011
ATLAS detected a new "quarkonium state" containing a beauty quark bound
with its antiquark.

Note:

CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 20 Member States.

After spending 19 weeks working in one place while solar power was too low for driving during the Martian winter, NASA's Mars Exploration Rover Opportunity is on the move again. The winter worksite was on the north slope of an outcrop called Greeley Haven. The rover used its rear hazard-avoidance camera after nearly completing the May 8 drive, capturing this view looking back at the Greeley Haven.

Since landing in the Meridiani region of Mars on Jan. 25, 2004, Universal Time and EST (Jan. 24, PST), Opportunity has driven 21.4 miles (34.4 kilometers).

This image is of Opportunity's traverse map from Sol 2951 and shows the entirety of the rover's travels to this point. A sol is a Martian day.

The strange galaxy Centaurus A is pictured in a new image from the European Southern Observatory. With a total exposure time of more than 50 hours this is probably the deepest view of this peculiar and spectacular object ever created. The image was produced by the Wide Field Imager of the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile.

Centaurus A, also known as NGC 5128 [1], is a peculiar massive elliptical galaxy with a supermassive black hole at its heart. It lies about 12 million light-years away in the southern constellation of Centaurus (The Centaur) and has the distinction of being the most prominent radio galaxy in the sky. Astronomers think that the bright nucleus, strong radio emission and jet features of Centaurus A are produced by a central black hole with a mass of about 100 million times that of the Sun. Matter from the dense central parts of the galaxy releases vast amounts of energy as it falls towards the black hole.

The strange galaxy Centaurus A in the constellation of Centaurus

This Wide Field Imager (WFI) picture allows us to appreciate the galaxy’s elliptical nature, which shows up as the elongated shape of the fainter outer parts. The glow that fills much of the picture comes from hundreds of billions of cooler and older stars. Unlike most elliptical galaxies, however, Centaurus A’s smooth shape is disturbed by a broad and patchy band of dark material that obscures the galaxy’s centre.

The dark band harbours large amounts of gas, dust and young stars. Bright young star clusters appear at the upper-right and lower-left edges of the band along with the red glow of star-forming clouds of hydrogen, whilst some isolated dust clouds are silhouetted against the stellar background. These features, and the prominent radio emission, are strong evidence that Centaurus A is the result of a merger between two galaxies. The dusty band is probably the mangled remains of a spiral galaxy in the process of being ripped apart by the gravitational pull of the giant elliptical galaxy.

Zooming in on the strange galaxy Centaurus A

The new set of images from WFI include long exposures through red, green and blue filters as well as filters specially designed to isolate the light from glowing hydrogen and oxygen. The latter help us to spot the known optical jet features around Centaurus A, which were barely visible in a previous image from the Wide Field Imager (eso0315a).

Extending from the galaxy to the upper left corner of the image are two groups of reddish filaments, which are roughly lined up with the huge jets that are prominent in radio images. Both sets of filaments are stellar nurseries, containing hot young stars [2]. Above the left side of the dusty band, we find the inner filaments, lying about 30 000 light-years away of the nucleus. Further out, around 65 000 light-years away from the galaxy’s nucleus and close to the upper left corner of the image, the outer filaments are visible. There is also possibly a very much fainter trace of a counter jet extending to the lower right.

Panning over a deep view at the strange galaxy Centaurus A

Centaurus A has been extensively studied at wavelengths ranging from radio all the way to gamma-rays. In particular, radio and X-ray observations have been crucial for studying the interaction between the energetic output of the central supermassive black hole and its surroundings, see eso0903. Studies of Centaurus A with ALMA are just beginning.

Many of the observations of Centaurus A used to make this image were taken to see whether it was possible to use ground-based surveys to detect and study variable stars in galaxies like Centaurus A outside the local group [3]. More than 200 new variable stars in Centaurus A were discovered.

Notes:

[1] The galaxy was first documented by British astronomer James Dunlop at the Parramatta observatory in Australia on August 4, 1826. This galaxy is often called Centaurus A because was the first major source of radio waves discovered in the constellation of Centaurus back in the 1950s.

[2] The origin of both filaments is not clear and astronomers still debate whether they are the result of the ionisation produced by radiation from the nucleus or the result of shocks within the gas clumps.

The year 2012 marks the 50th anniversary of the founding of the European Southern Observatory (ESO). ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 40-metre-class European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Observations with NASA's Chandra X-ray Observatory have provided the first X-ray evidence of a supernova shock wave breaking through a cocoon of gas surrounding the star that exploded. This discovery may help astronomers understand why some supernovas are much more powerful than others.

On Nov. 3, 2010, a supernova was discovered in the galaxy UGC 5189A, located about 160 million light years away. Using data from the All Sky Automated Survey telescope in Hawaii taken earlier, astronomers determined this supernova exploded in early October 2010 (in Earth's time-frame).

This composite image of UGC 5189A shows X-ray data from Chandra in purple and optical data from Hubble Space Telescope in red, green and blue. SN 2010jl is the very bright X-ray source near the top of the galaxy.

A team of researchers used Chandra to observe this supernova in December 2010 and again in October 2011. The supernova was one of the most luminous that has ever been detected in X-rays.

In optical light, SN 2010jl was about ten times more luminous than a typical supernova resulting from the collapse of a massive star, adding to the class of very luminous supernovas that have been discovered recently with optical surveys. Different explanations have been proposed to explain these energetic supernovas including (1) the interaction of the supernova's blast wave with a dense shell of matter around the pre-supernova star, (2) radioactivity resulting from a pair-instability supernova (triggered by the conversion of gamma rays into particle and anti-particle pairs), and (3) emission powered by a neutron star with an unusually powerful magnetic field.

Chandra X-ray Observatory

In the first Chandra observation of SN 2010jl, the X-rays from the explosion's blast wave were strongly absorbed by a cocoon of dense gas around the supernova. This cocoon was formed by gas blown away from the massive star before it exploded.

In the second observation taken almost a year later, there is much less absorption of X-ray emission, indicating that the blast wave from the explosion has broken out of the surrounding cocoon. The Chandra data show that the gas emitting the X-rays has a very high temperature -- greater than 100 million degrees Kelvin – strong evidence that it has been heated by the supernova blast wave.

The energy distribution, or spectrum, of SN 2010jl in optical light reveals features that the researchers think are explained by the following scenario: matter around the supernova has been heated and ionized (electrons stripped from atoms) by X-rays generated when the blast wave plows through this material. While this type of interaction has been proposed before, the new observations directly show, for the first time, that this is happening.

This discovery therefore supports the idea that some of the unusually luminous supernovas are caused by the blast wave from their explosion ramming into the material around it.

In a rare example of a cosmic coincidence, analysis of the X-rays from the supernova shows that there is a second unrelated source at almost the same location as the supernova. These two sources strongly overlap one another as seen on the sky. This second source is likely to be an ultraluminous X-ray source, possibly containing an unusually heavy stellar-mass black hole, or an intermediate mass black hole.

These results were published in a paper appearing in the May 1st, 2012 issue of The Astrophysical Journal Letters. The authors were Poonam Chandra (Royal Military College of Canada, Kingston, Canada), Roger Chevalier and Christopher Irwin (University of Virginia, Charlottsville, VA), Nikolai Chugai (Institute of Astronomy of Russian Academy of Sciences, Moscow, Russia), Claes Fransson (Stockholm University, Sweden), and Alicia Soderberg (Harvard-Smithsonian Center for Astrophysics, Cambridge, MA).

mardi 15 mai 2012

Early this morning, an Ariane 5 launcher lifted off from Europe’s Spaceport in French Guiana on its mission to place two telecommunications satellites, JCSAT-13 and Vinasat-2, into their planned transfer orbits.

Liftoff of Ariane VA206

Liftoff of flight VA206, the 62nd Ariane 5 mission, came at 22:13 GMT (00:13 CEST; 19:13 French Guiana). The target injection orbit had a perigee altitude of 249.9 km, an apogee altitude at injection of 35 911 km and an inclination of 2°.

The satellites were accurately injected into their transfer orbits about 26 minutes and 36 minutes after liftoff, respectively.

JCSAT-13 will be positioned above the equator at 124°E. It will deliver
direct TV broadcast links to Japan and will meet satellite demands in
Southeast Asia.

JCSAT-13

Vinasat-2, to be positioned at 131.8°E, will provide radio, television and telephone links to Vietnam.

Vinasat-2

The payload mass for this launch was 8381 kg; the satellites totalled 7563 kg, with payload adapters and dispensers making up the additional 818 kg.

VA204 flight timeline

Ariane 5’s cryogenic, liquid-propellant main engine was ignited first. Seven seconds later, the solid-propellant boosters also fired, and the vehicle lifted off a fraction of a second later.

The solid boosters were jettisoned 2 min 25 sec after main engine ignition, and the fairing protecting the payload during the climb through Earth’s atmosphere was discarded at 3 min 11 sec.

The launcher’s main engine shut down at 8 min 54 sec; six seconds later, the main cryogenic stage separated from the upper stage and its payload.

Upper stage and its payload

Four seconds after main stage separation, the engine of the cryogenic upper stage ignited to continue the journey. The engine shut down at 25 min 01 sec into the flight, at which point the vehicle was travelling at 9339 m/s (33 620.4 km/h) at an altitude of 669.9 km. The conditions for geostationary transfer orbit injection had been achieved.

Less than 10 minutes after launch their Soyuz TMA-04M spacecraft reached orbit, and its antennas and solar arrays deployed.

Also onboard with the crew, was a small Smokey Bear plush serving as the traditional Soyuz “talisman.” Smokey Bear is the national symbol for wildfire prevention. Preflight, Acaba explained he proposed flying Smokey in an effort to raise awareness of human-caused wildfires.

This Smokey Bear plush toy is accompanying Flight Engineer Joe Acaba and his Soyuz crewmates on the trip to the International Space Station. Credit: U.S. Forest Service.

The trio will dock to the station’s Poisk Mini-Research Module at 12:38 a.m. Thursday, bringing the Expedition 31 crew to its full six-member complement. Acaba, Revin and Padalka will join the current station residents, Commander Oleg Kononenko and Flight Engineers Don Pettit and Andre Kuipers, and begin a four-month tour of duty aboard the orbiting complex.

Kononenko, Pettit and Kuipers, who arrived Dec. 23 aboard their Soyuz TMA-03M spacecraft, will return home on July 1, marking the start of Expedition 32 under the command of Padalka. About two weeks afterward, NASA astronaut Suni Williams, Russian cosmonaut Yuri Malenchenko and Japan Aerospace Exploration Agency astronaut Aki Hoshide will arrive at the orbiting complex to round out the Expedition 32 crew.

Acaba previously visited the station in March 2009 as a mission specialist for the STS-119 crew aboard space shuttle Discovery. The crew delivered the final set of solar array wings and truss element to complete the station’s electricity-generating system. Acaba accumulated 12 hours, 57 minutes of spacewalk time during two excursions outside the station during STS-119.

This will mark Padalka’s fourth long-duration spaceflight and his third aboard the station. He previously completed 198 days in space aboard Mir in February 1999 and served as station commander for Expedition 9 in 2004 and Expedition 19/20 in 2009. Revin is making his first trip into space.

After more than a decade in orbit, ESA’s Proba-1 was showing its age – even hibernating last winter. But a software fix to its startracker, radiation-impaired after surpassing its design lifetime fivefold, has returned the veteran Earth-observing microsatellite to full operation.

New software from the Technical University of Denmark (DTU) allows Proba-1 to distinguish between genuine star constellations to measure its pointing direction versus clusters of radiation-induced ‘hotspots’.

Proba-1 in orbit

“The result is that Proba-1’s startracker is practically rejuvenated,” said Frederic Teston, head of ESA’s Proba programme. “The mission is back in business.”

Its name standing for ‘Project for Onboard Autonomy’, Proba-1 was designed for autonomous operations when it entered low-Earth orbit on 22 October 2001.

Ground controllers at ESA’s Redu centre in Belgium only need to supply geographical coordinates of a ground target and the microsatellite – smaller than a cubic metre – steers itself into the appropriate position, even tilting to acquire multi-angular views.

The problem was that years of continuous bombardment by the charged particles permeating space built up bright points on the CCD that began to camouflage actual stars.

“Such hotspots correspond to single pixels, while stars extend beyond single pixels exhibiting lens effects,” explained Troelz Denver, associate professor at DTU. “So to begin with it was quite simple to distinguish the two classes.

Hotspot clusters hide stars

“The challenge comes as radiation hits accumulate, having two, three or more adjacent pixels impaired. Proba-1 ended up perceiving three to four times more hotspots clusters than stars.”

The radiation effects show up more strongly on the CCD as temperatures increase. So Proba-1 went into hibernation last January, when (counter-intuitively for those in the northern hemisphere) Earth’s elliptical orbit takes it closest to the Sun – and the intensity of sunlight on the satellite increases by 10%.

But while Proba-1 was developed as a technology demonstrator with a two-year lifetime, it has evolved into an operational Earth observation mission. Hundreds of scientific teams worldwide were inconvenienced by any observation gap.

CHRIS image of Pretoria, South Africa

“We kept in close touch with the ESA Redu team and the mission’s prime contractor QinetiQ Space,” added Dr Denver. “A fix was possible because the ASC is completely reprogrammable in flight.

“Redu performed manoeuvres trying to decrease the startracker temperature, while they supplied imagery from the instrument for testing – we could see just what the tracker was seeing.

“The new algorithms developed made use of the fact that Proba-1’s ASC has two camera heads –preventing the Sun or Earth blocking out views of the stars along a single direction.

Twin startracker camera heads

“When one head has difficulties isolating the stars from the hotspot clusters, it’s now being assisted by the other.”

The improved algorithm is also available for use on subsequent ASC versions, which has flown on ESA’s Smart-1 Moon mission, the Sun-monitoring Proba-2, gravity-mapping GOCE and the soon-to-be launched Swarm satellite constellation to chart Earth’s magnetic field.

DTU originally developed the ASC for Denmark’s national Ørsted satellite in the 1990s. One particular requirement was the ability to autonomously fix its orientation even when out of control –‘lost-in-space’.

Proba-1 HRC image of Turkmenistan

Dr Denver envisages future space missions flying multiple startracker cameras: “The more heads aboard, the more complex manoeuvres can be exercised without blinding the spacecraft. And, as Proba-1 shows, the startracker’s working life is boosted.”